Mobile telecommunications service providers increasingly use Wi-Fi® networks to offload carrier based network traffic using Internet protocol multimedia services (IMS) such as Wi-Fi calling or Voice over Wi-Fi (VoWi-Fi) services. Wi-Fi networks can be operated by the mobile telecommunications service providers (carrier-operated public Wi-Fi networks) or by independent network operators (e.g., home and enterprise Wi-Fi networks). From a data traffic point of view, Wi-Fi networks can be classified as trusted and untrusted Wi-Fi networks.
Wi-Fi calling or Voice over Wi-Fi (VoWi-Fi) services may use 3rd Generation Partnership Project (3GPP) untrusted wireless local area network (WLAN) access integration to the evolved packet core (EPC) network. The 3GPP untrusted WLAN access integration uses evolved packet data gateway (ePDG) devices for access to the EPC from WLAN or Wi-Fi networks.
From a network operator perspective, a carrier-operated public Wi-Fi network can be classified as a trusted WLAN access network because the same network operator controls the Wi-Fi network and the 3GPP network. However, from a VoWi-Fi enabled device's perspective, all non-3GPP access networks including any type of WLAN such as home, enterprise and carrier-operated public Wi-Fi networks are untrusted and insecure Communication via untrusted and insecure WLANs is typically encrypted and a Quality of Service (QoS) cannot be guaranteed.